1. Field of the Invention
The present invention relates to a communication method, a communication system and a computer readable recording medium recording a communication program for a communication network in which a plurality of equipments allowing communication with each other are connected. More specifically, the present invention relates to a communication method, a communication system and a computer readable recording medium recording a communication program in which various information including functions of a plurality of equipments connected to the communication network can be shared by respective equipments.
2. Description of the Background Art
Japanese Patent Laying-Open No. 8-19060 discloses an AV (Audio Visual) equipment control system to which a plurality of AV equipments are connected for communication and which allows operation of these equipments collectively. In the AV equipment control system, when a new AV equipment is connected to the system, the new AV equipment transmits a control object to a control apparatus controlling each of the AV equipments. At this time, the new AV equipment must first designate an address of the control apparatus and then transmit the control object. Similarly, when the control apparatus controls each of the AV equipments connected to the system, an address or ID (Identification) for designating each AV equipment must be known in advance.
When a plurality of AV equipments are to be controlled, an address designation of "ALL" is allowed, which address designation is for controlling all the AV equipments connected.
In the AV equipment control system described in the aforementioned laid-open paten application, it is necessary for the control apparatus to know in advance correspondence between functions of respective AV equipments and the addresses or IDs of the AV equipments, by incorporating a table of correspondence. When the number of AV equipments is small, it is easy for the control apparatus to know or comprehend the addresses, IDs and functions utilizing a table. However, when the number of AV equipments is very large or when each AV equipment may serve as a control apparatus as well as a controlled apparatus, it is extremely difficult to comprehend all the addresses, IDs and functions of those AV equipments which may also function as control apparatus, by utilizing a table. Further, when a control apparatus is newly added or omitted, the address, ID or function of the added or omitted control apparatus must be added to or deleted from the table in each AV equipment, which results in troublesome table management.
In AV equipment designation using an ID or an address, individual AV equipment may be designated, or all AV equipments may be designated. Therefore, when television image display by an AV equipment capable of outputting the television image is desired, a packet is individually transmitted to every AV equipment inquiring whether it has television image output function, and thereafter, a control packet for television image output is transmitted again individually to those AV equipments which have the television image output function. Therefore, the number of packets in transmission paths is considerably large, and therefore efficiency in communication and control is not very high.
Recently, the number of electrical appliances or equipments for home use has been increasing. Therefore, a system for controlling all the electrical appliances for home use through a communication network has been desired. In order to control various electrical appliances or equipments, a method of managing respective addresses of the equipments is necessary. However, preparation of a management table is troublesome. Further, in a home network, it is not practical to provide a centralized managing equipment. However, when management tables are managed in decentralized manner by respective equipments, management would be very troublesome.